Trip Generation Characteristics of Free-Standing Discount Superstores

Institute of Transportation Engineers. ITE Journal, Aug 2006 by Vivian, Georgiena M

FREE-STANDING DISCOUNT SUPERSTORES HAVE GAINED IN POPULARITY BECAUSE OF THEIR CONVENIENCE, COMBINING GENERAL RETAIL MERCHANDISE, FULL-SERVICE GROCERY DEPARTMENTS AND OTHER SPECIALTY SHOPS AT DISCOUNT RATES. THIS STUDY SHOWED A P.M. PEAK-HOUR TRIP GENERATION RATE OF 5.50, SUBSTANTIALLY HIGHER THAN THE STANDARD ITE FREE-STANDING DISCOUNT SUPERSTORE P.M. PEAK-HOUR RATE OF 3.87.

IN THE PAST DECADE, THE NUMber of proposed free-standing discount superstores has increased throughout the United States. These stores have continued to gain in popularity because of their convenience, combining general retail merchandise, full-service grocery departments and other specialty shops, such as pharmacies and photo processing, at discount rates.

Due to this popularity, many localities are growing concerned over the impact of these stores on their communities and infrastructure system. Regarding traffic impacts, an important issue has been raised concerning whether the published Institute of Transportation Engineers (ITE) trip generation rates for free-standing discount superstores are accurate for superstores that are larger than the average facilities documented in Trip Generation.

This feature provides a summary of a trip generation study prepared for a major discount superstore company located throughout the United States by looking at traffic conditions related to five freestanding discount superstores.

INTRODUCTION

Trip generation for traffic impact analyses typically is conducted using trip generation rates published by ITE. For most retail land uses, traffic impacts are focused on the p.m. peak-hour of adjacent street traffic to determine the needed infrastructure improvements surrounding the store.

In the case of free-standing discount superstores, the published trip generation rates are based on surveys conducted during the 1990s and 2000 throughout the United States.

It is believed that larger superstores may generate at different rates. It should be noted that: only 10 stores were surveyed for the ITE rate; the average size of the stores surveyed in determining the ITE rate was 161,000 square feet, although many of today's free-standing discount superstores have more than 200,000 square feet (213,210 for purposes of this study); and free-standing discount superstores intuitively should have a higher trip generation rate than free-standing discount stores, which by definition do not contain a full-service grocery store but have most of the other amenities of the superstore.

This study was undertaken to provide additional information regarding the issues noted above. The principal question to be addressed in the study was whether today's free-standing discount superstores with sizes greater than 200,000 square feet have different trip generation characteristics than the freestanding discount superstores averaging 161,000 square feet, which were sources of data for ITE Land Use Code 813. The current ITE category used for a freestanding discount superstore is Land Use Code 813.

Discount superstores arc free-standing stores with off-street parking. They offer a variety of customer services and centralized cashiering and contain a fullservice grocery department under the same roof that shares entrances and exits with the discount superstore area. They typically maintain long store hours, seven days a week.

The stores included in this land use often are the only ones on the site, but they also can be found in mutual operation with a related or unrelated garden center and/or service station. They sometimes are found as separate parcels within a retail complex with their own dedicated parking area. Land Use Code 815 (free-standing discount store) is a related use.

Table 1 depicts the ITE published average daily weekday rate of traffic and the p.m. peak-hour rate of adjacent street traffic for a free-standing discount superstore per 1,000 square feet of gross floor area (GFA). Per the discussion, Table 1 also includes the rate for Land Use Code 815 for comparison.

In addition to the use of the free-standing discount superstore, often when part of a larger retail development, traffic impact analysis will be conducted using the ITE rate for Land Use Code 820 (shopping center). For discussion purposes, the shopping center rate also is included in Table 1.

METHODOLOGY

This study included five stores in the states of Oklahoma and Texas that fit the ITE definition of free-standing discount superstore to estimate their peak-hour trip generation. Field review of all locations included a sketch-level drawing of the site plan, including the driveways to be counted at each location.

Each building's square footage was attained and calculated either by site plans obtained from each local jurisdiction in which the superstore was located, by a measuring wheel during field review, or by contact with the store. The square footage of the garden center and tire and lube shop were included in the square footage calculations.

Staff were positioned at the driveway openings and traffic counts at each of the facilities were conducted on two typical weekdays (Tuesday, Wednesday and/or Thursday) from 4:00 p.m. to 6:00 p.m. The first weekday count was taken in July 2003 and the second in October 2003. It should be noted that no inclement weather occurred during either season of the traffic counts. The peak hour of adjacent traffic was determined to be from 4:30 p.m. to 5:30 p.m. and was used for analysis purposes.